How AI May Transform Musculoskeletal Imaging.

While musculoskeletal imaging volumes are increasing, there is a relative shortage of subspecialized musculoskeletal radiologists to interpret the studies. Will artificial intelligence (AI) be the solution? For AI to be the solution, the wide implementation of AI-supported data acquisition methods in clinical practice requires establishing trusted and reliable results. This implementation will demand close collaboration between core AI researchers and clinical radiologists. Upon successful clinical implementation, a wide variety of AI-based tools can improve the musculoskeletal radiologist's workflow by triaging imaging examinations, helping with image interpretation, and decreasing the reporting time. Additional AI applications may also be helpful for business, education, and research purposes if successfully integrated into the daily practice of musculoskeletal radiology. The question is not whether AI will replace radiologists, but rather how musculoskeletal radiologists can take advantage of AI to enhance their expert capabilities.

Erosive hand osteoarthritis and sarcopenia: data from Osteoarthritis Initiative cohort.

OBJECTIVES: There is no evidence linking specific osteoarthritis (OA) types, such as erosive hand OA (EHOA), with distant generalised changes in muscle composition (sarcopenia), which can potentially be modified. This study pioneers the exploration of the association between EHOA and sarcopenia, both of which are predominantly observed in the older adults. METHODS: Using the Osteoarthritis Initiative cohort, we selected hand OA (modified Kellgren and Lawrence (grade ≥2 in ≥1 hand joint) participants with radiographic central erosions in ≥1 joints (EHOA group) and propensity score-matched hand OA participants with no erosion (non-EHOA group). MRI biomarkers of thigh muscles were measured at baseline, year 2 and year 4 using a validated deep-learning algorithm. To adjust for 'local' effects of coexisting knee OA (KOA), participants were further stratified according to presence of radiographic KOA. The outcomes were the differences between EHOA and non-EHOA groups in the 4-year rate of change for both intramuscular adipose tissue (intra-MAT) deposition and contractile (non-fat) area of thigh muscles. RESULTS: After adjusting for potential confounders, 844 thighs were included (211 EHOA:633 non-EHOA; 67.1±7.5 years, female/male:2.9). Multilevel mixed-effect regression models showed that EHOA is associated a different 4-year rate of change in intra-MAT deposition (estimate, 95% CI: 71.5 mm2/4 years, 27.9 to 115.1) and contractile area (estimate, 95% CI: -1.8%/4 years, -2.6 to -1.0) of the Quadriceps. Stratified analyses showed that EHOA presence is associated with adverse changes in thigh muscle quality only in participants without KOA. CONCLUSIONS: EHOA is associated with longitudinal worsening of thigh muscle composition only in participants without concomitant KOA. Further research is needed to understand the systemic factors linking EHOA and sarcopenia, which unlike EHOA is modifiable through specific interventions.

Osteoarthritis year in review 2023: Imaging.

PURPOSE: This narrative review summarizes the original research in the field of in vivo osteoarthritis (OA) imaging between 1 January 2022 and 1 April 2023. METHODS: A PubMed search was conducted using the following several terms pertaining to OA imaging, including but not limited to "Osteoarthritis / OA", "Magnetic resonance imaging / MRI", "X-ray" "Computed tomography / CT", "artificial intelligence /AI", "deep learning", "machine learning". This review is organized by topics including the anatomical structure of interest and modality, AI, challenges of OA imaging in the context of clinical trials, and imaging biomarkers in clinical trials and interventional studies. Ex vivo and animal studies were excluded from this review. RESULTS: Two hundred and forty-nine publications were relevant to in vivo human OA imaging. Among the articles included, the knee joint (61%) and MRI (42%) were the predominant anatomical area and imaging modalities studied. Marked heterogeneity of structural tissue damage in OA knees was reported, a finding of potential relevance to clinical trial inclusion. The use of AI continues to rise rapidly to be applied in various aspect of OA imaging research but a lack of generalizability beyond highly standardized datasets limit interpretation and wide-spread application. No pharmacologic clinical trials using imaging data as outcome measures have been published in the period of interest. CONCLUSIONS: Recent advances in OA imaging continue to heavily weigh on the use of AI. MRI remains the most important modality with a growing role in outcome prediction and classification.

A perspective on the evolution of semi-quantitative MRI assessment of osteoarthritis: Past, present and future.

OBJECTIVE: This perspective describes the evolution of semi-quantitative (SQ) magnetic resonance imaging (MRI) in characterizing structural tissue pathologies in osteoarthritis (OA) imaging research over the last 30 years. METHODS: Authors selected representative articles from a PubMed search to illustrate key steps in SQ MRI development, validation, and application. Topics include main scoring systems, reading techniques, responsiveness, reliability, technical considerations, and potential impact of artificial intelligence (AI). RESULTS: Based on original research published between 1993 and 2023, this article introduces available scoring systems, including but not limited to Whole-Organ Magnetic Resonance Imaging Score (WORMS) as the first system for whole-organ assessment of the knee and the now commonly used MRI Osteoarthritis Knee Score (MOAKS) instrument. Specific systems for distinct OA subtypes or applications have been developed as well as MRI scoring instruments for other joints such as the hip, the fingers or thumb base. SQ assessment has proven to be valid, reliable, and responsive, aiding OA investigators in understanding the natural history of the disease and helping to detect response to treatment. AI may aid phenotypic characterization in the future. SQ MRI assessment's role is increasing in eligibility and safety evaluation in knee OA clinical trials. CONCLUSIONS: Evidence supports the validity, reliability, and responsiveness of SQ MRI assessment in understanding structural aspects of disease onset and progression. SQ scoring has helped explain associations between structural tissue damage and clinical manifestations, as well as disease progression. While AI may support human readers to more efficiently perform SQ assessment in the future, its current application in clinical trials still requires validation and regulatory approval.

Artificial intelligence in osteoarthritis detection: A systematic review and meta-analysis.

OBJECTIVES: As an increasing number of studies apply artificial intelligence (AI) algorithms in osteoarthritis (OA) detection, we performed a systematic review and meta-analysis to pool the data on diagnostic performance metrics of AI, and to compare them with clinicians' performance. MATERIALS AND METHODS: A search in PubMed and Scopus was performed to find studies published up to April 2022 that evaluated and/or validated an AI algorithm for the detection or classification of OA. We performed a meta-analysis to pool the data on the metrics of diagnostic performance. Subgroup analysis based on the involved joint and meta-regression based on multiple parameters were performed to find potential sources of heterogeneity. The risk of bias was assessed using Prediction Model Study Risk of Bias Assessment Tool reporting guidelines. RESULTS: Of the 61 studies included, 27 studies with 91 contingency tables provided sufficient data to enter the meta-analysis. The pooled sensitivities for AI algorithms and clinicians on internal validation test sets were 88% (95% confidence interval [CI]: 86,91) and 80% (95% CI: 68,88) and pooled specificities were 81% (95% CI: 75,85) and 79% (95% CI: 80,85), respectively. At external validation, the pooled sensitivity and specificity for AI algorithms were 94% (95% CI: 90,97) and 91% (95% CI: 77,97), respectively. CONCLUSION: Although the results of this meta-analysis should be interpreted with caution due to the potential pitfalls in the included studies, the promising role of AI as a diagnostic adjunct to radiologists is indisputable.

Thigh muscle composition changes in knee osteoarthritis patients during weight loss: Sex-specific analysis using data from osteoarthritis initiative.

OBJECTIVES: Sex of patients with knee osteoarthritis (KOA) may impact changes in thigh muscle composition during weight loss, the most well-known disease-modifying intervention. We investigated longitudinal sex-based changes in thigh muscle quality during weight loss in participants with KOA. METHODS: Using Osteoarthritis Initiative (OAI) cohort data, we included females and males with baseline radiographic KOA who experienced > 5 % reduction in Body Mass Index (BMI) over four years. Using a previously validated deep-learning algorithm, we measured Magnetic Resonance Imaging (MRI)-derived biomarkers of thigh muscles at baseline and year-4. Outcomes were the intra- and inter-muscular adipose tissue (Intra-MAT and Inter-MAT) and contractile percentage of thigh muscles between females and males. The analysis adjusted for potential confounders, such as demographics, risk factors, BMI change, physical activity, diet, and KOA status. RESULTS: A retrospective selection of available thigh MRIs from KOA participants who also had a 4-year weight loss (>5 % of BMI) yielded a sample comprising 313 thighs (192 females and 121 males). Female and male participants exhibited a comparable degree of weight loss (females: -9.72 ± 4.38, males: -8.83 ± 3.64, P-value=0.060). However, the changes in thigh muscle quality were less beneficial for females compared to males, as shown by a less degree of longitudinal decrease in Intra-MAT (change difference,95 %CI: 783.44 mm2/4-year, 505.70 to 1061.19, P-value<0.001) and longitudinal increase in contractile percentage (change difference,95 %CI: -3.9 %/4-year, -6.5 to -1.4, P-value=0.019). CONCLUSIONS: In participants with KOA and 4-year weight loss, the longitudinal changes in thigh muscle quality were overall beneficial but to a less degree in females compared to males. Further research is warranted to investigate the underlying mechanisms and develop sex-specific interventions to optimize muscle quality during weight loss.

Adiposity and cartilage lesions following ACL reconstruction.

OBJECTIVE: To determine if global, central, or peripheral adiposity is associated with prevalent and worsening cartilage lesions following anterior cruciate ligament reconstruction (ACLR). METHODS: In 107 individuals one-year post-ACLR, adiposity was assessed globally (body mass index), centrally (waist circumference), and peripherally (knee subcutaneous adipose tissue thickness) from magnetic resonance imaging (MRI). Tibiofemoral and patellofemoral cartilage lesions were assessed from knee MRIs at 1- and 5-years post-ACLR. Poisson regression evaluated the relation of adiposity with prevalent and worsening tibiofemoral and patellofemoral cartilage lesions adjusting for age, sex, and activity level. RESULTS: The prevalence ratios of adiposity with tibiofemoral (presence in 49%) and patellofemoral (44%) cartilage lesions ranged from 0.99 to 1.03. Adiposity was more strongly associated with longitudinal changes in tibiofemoral (worsening in 21%) and patellofemoral (44%) cartilage lesions. One-unit increase in global (kg/m2), central (cm), and peripheral (mm) adiposity was associated with a higher risk of worsening tibiofemoral cartilage lesions by 17% (risk ratios [95% confidence interval (CI)]: 1.17 [1.09 to 1.23]), 5% (1.05 [1.02 to 1.08]), and 9% (1.09 [1.03 to 1.16]), and patellofemoral cartilage lesions by 5% (1.05 [1.00 to 1.12]), 2% (1.02 [1.00 to 1.04]) and 2% (1.02 [1.00 to 1.04]), respectively. CONCLUSION: Greater adiposity was a risk factor for worsening cartilage lesions up to 5 years post-ACLR. Clinical interventions aimed at mitigating excess adiposity may be beneficial in preventive approaches for early post-traumatic osteoarthritis.

Causal relationships between pain, medical treatments, and knee osteoarthritis: A graphical causal model to guide analyses.

OBJECTIVE: Randomized controlled trials (RCTs) are a gold standard for estimating the benefits of clinical interventions, but their decision-making utility can be limited by relatively short follow-up time. Longer-term follow-up of RCT participants is essential to support treatment decisions. However, as time from randomization accrues, loss to follow-up and competing events can introduce biases and require covariate adjustment even for intention-to-treat effects. We describe a process for synthesizing expert knowledge and apply this to long-term follow-up of an RCT of treatments for meniscal tears in patients with knee osteoarthritis (OA). METHODS: We identified 2 post-randomization events likely to impact accurate assessment of pain outcomes beyond 5 years in trial participants: loss to follow-up and total knee replacement (TKR). We conducted literature searches for covariates related to pain and TKR in individuals with knee OA and combined these with expert input. We synthesized the evidence into graphical models. RESULTS: We identified 94 potential covariates potentially related to pain and/or TKR among individuals with knee OA. Of these, 46 were identified in the literature review and 48 by expert panelists. We determined that adjustment for 50 covariates may be required to estimate the long-term effects of knee OA treatments on pain. CONCLUSION: We present a process for combining literature reviews with expert input to synthesize existing knowledge and improve covariate selection. We apply this process to the long-term follow-up of a randomized trial and show that expert input provides additional information not obtainable from literature reviews alone.

Imaging Biomarkers of Osteoarthritis.

Currently no disease-modifying osteoarthritis drug has been approved for the treatment of osteoarthritis (OA) that can reverse, hold, or slow the progression of structural damage of OA-affected joints. The reasons for failure are manifold and include the heterogeneity of structural disease of the OA joint at trial inclusion, and the sensitivity of biomarkers used to measure a potential treatment effect.This article discusses the role and potential of different imaging biomarkers in OA research. We review the current role of radiography, as well as advances in quantitative three-dimensional morphological cartilage assessment and semiquantitative whole-organ assessment of OA. Although magnetic resonance imaging has evolved as the leading imaging method in OA research, recent developments in computed tomography are also discussed briefly. Finally, we address the experience from the Foundation for the National Institutes of Health Biomarker Consortium biomarker qualification study and the future role of artificial intelligence.

Quantitative CT lumbar spine BMD cutpoint value for classifying osteoporosis among older Chinese men can be the same as that of older Chinese women, both much lower than the value for Caucasians.

For older Caucasian women and men, the QCT (quantitative CT) lumbar spine (LS) bone mineral density (BMD) threshold for classifying osteoporosis is 80 mg/ml. It was recently proposed that, for older East Asian women, the QCT LS BMD value equivalent to the Caucasian women's threshold of 80 mg/mL is about 45∼50 mg/ml. For a data of 328 cases of Chinese men (age: 73.6 ± 4.4 years) who had QCT LS BMD and DXA LS BMD at the same time and with the DXA BMD value of ≤ 0.613 g/cm2 to classify osteoporosis, the corresponding QCT LS BMD threshold is 53 mg/ml. Osteoporotic-like vertebral fracture sum score (OLVFss) ≤ -2.5 has been proposed to diagnose osteoporosis. For 316 cases of Chinese men (age:73.7±4.5 years), OLVFss ≤ -2.5 defines an osteoporosis prevalence of 4.4%; to achieve this osteoporosis prevalence, the corresponding QCT LS BMD value is < 47.5 mg/ml. In the China Action on Spine and Hip Status study, a Genant grades 2/3 radiographic 'osteoporotic vertebral fracture' prevalence was 2.84% for Chinese men (total n = 1267, age: 62.77 ± 9.20 years); to achieve this osteoporosis prevalence, the corresponding BMD value was < 42.5 mg/ml. In a study of 357 Beijing older men, according to the clinical fragility fracture prevalence and femoral neck DXA T-score, the QCT LS BMD value to classify osteoporosis was between 39.45 mg/ml and 51.38 mg/ml. For older Chinese men (≥ 50 years), we recommend the cutpoint for the QCT LS BMD definition of osteoporosis to be 45∼50 mg/ml which is the same as the value for Chinese women.

Much lower prevalence and severity of spine degenerative changes among older Chinese women than among older Caucasian women and its implication for the interpretation of lumbar spine BMD T-score for Chinese women.

The prevalence and severity of spine degenerative changes have been noted to be lower among older Chinese women than among older Caucasian women. Spine degenerative changes associated with marginal osteophytosis, trabecular thickening, subchondral sclerosis, facet joint arthrosis, and disc space narrowing can all lead to artificially higher spine areal bone mineral density (BMD). The lower prevalence and severity of spine degeneration have important implications for the interpretation of spine areal BMD reading for Chinese women. With fewer contributions from spine degenerative changes, following natural aging, the declines of population group means of spine BMD and T-score are faster for Chinese women than for Caucasian women. While a cutpoint T-score ≤ -2.5 for defining spine densitometric osteoporosis is recommended for Caucasian women, for Chinese women the same cutpoint T-score of ≤ -2.5 inflates the estimated osteoporosis prevalence based on spine BMD measure. In addition to the use of an ethnicity-specific BMD reference database, a stricter cutpoint T-score for defining spine densitometric osteoporosis among older Chinese women should be applied.

Quantitative CT lumbar spine BMD cutpoint value for classifying osteoporosis among older East Asian women should be lower than the value for Caucasians.

For Caucasian women, the QCT (quantitative CT) lumbar spine (LS) bone mineral density (BMD) cutpoint value for classifying osteoporosis is 80 mg/ml. At the age of approximate 78 years, US Caucasian women QCT LS BMD population mean is 80 mg/ml, while that of Chinese women and Japanese women is around 50 mg/ml. Correlation analyses show, for Chinese women and Japanese women, QCT LS BMD of 45 mg/ml corresponds to the dual-energy X-ray absorptiometry cutpoint value for classifying osteoporosis. For Chinese and Japanese women, if QCT LS BMD 80 mg/ml is used as the threshold to classify osteoporosis, then the specificity of classifying subjects with vertebral fragility fracture into the osteoporotic group is low, whereas threshold of 45 mg/ml approximately achieve a similar separation for women with and without vertebral fragility fracture as the reports for Caucasian women. Moreover, by using 80mg/ml as the cutpoint value, LS QCT leads to excessively high prevalence of osteoporosis for Chinese women, with the discordance between hip dual-energy X-ray absorptiometry and LS QCT measures far exceeding expectation. Considering the different bone properties and the much lower prevalence of fragility fractures in the East Asian women compared with Caucasians, we argue that the QCT cutpoint value for classifying osteoporosis among older East Asian women will be close to and no more than 50 mg/ml LS BMD. We suggest that it is also imperative the QCT osteoporosis classification criterion for East Asian male LS, and male and female hips be re-examined.

Transcatheter arterial tendinopathy embolization as a treatment for painful and refractory tendinopathy: a systematic review and meta-analysis.

OBJECTIVE: Transcatheter arterial embolization (TAE) is a novel minimally invasive therapy for painful tendinopathy in patients with pain refractory to conservative management. The purpose of this study was to evaluate evidence on the efficacy of TAE for tendinopathy related pain. MATERIALS AND METHODS: Using Embase, PubMed, and Web of Science, a systematic review and meta-analysis was performed to identify studies evaluating TAE for painful tendinopathy. The primary outcome measure was change in pain scale score at 6 months. A Ratio of Means (ROM) was used to compare the effect size post treatment as compared to baseline. The Visual Analog Scale (VAS) was used as the metric for comparison. RESULTS: After screening titles, abstracts, and the full text, 5 studies met inclusion criteria. A total of 97 tendinopathy embolization procedures performed in 74 patients were included. Patients who underwent TAE demonstrated declines in VAS ROM at 1 day 0.53 [95% CI 0.31,0.88], 1 week (0.51 [95% CI 0.32,0.79]), 1 month (0.45 [95% CI 0.29, 0.71]), 3-4 months (0.33 [95% CI 0.22,0.48]), and 6 months following embolization (0.18[95% CI 0.13,0.26]), respectively. DISCUSSION: TAE provides substantial short-term reductions in pain scores for patients suffering with refractory tendinopathy related pain of the rotator cuff, elbow extensor and flexor, Achilles, and patellar tendons.

East Asians' T-scores for the diagnosis of osteoporosis should be calculated using ethnicity- and gender-specific BMD reference ranges: justifications.

The 2013 ISCD consensus recommended a Caucasian female reference database for T-score calculation in men, which says "A uniform Caucasian (non-race adjusted) female reference database should be used to calculate T-scores for men of all ethnic groups." However, this statement was recommended for the US population, and no position was taken with respect to BMD reference data or ethnicity matching outside of the USA. In East Asia, currently, a Japanese BMD reference database is universally adopted in Japan for clinical DXA diagnosis, while both local BMD and Caucasian BMD reference databases are in use in Mainland China, South Korea, Taiwan, and Singapore. In this article, we argue that an ethnicity- and gender-specific BMD database should be used for T-score calculations for East Asians, and we list the justifications why we advocate so. Use of a Caucasian BMD reference database leads to systematically lower T-scores for East Asians and an overestimation of the prevalence of osteoporosis. Using a female BMD reference database to calculate T-scores for male patients leads to higher T-score values and an underestimation of the prevalence of osteoporosis. Epidemiological evidence does not support using a female BMD reference database to calculate T-scores for men. We also note that BMD reference databases collected in Asia should be critically evaluated for their quality.

Automated weight-bearing foot measurements using an artificial intelligence-based software.

OBJECTIVE: To assess the accuracy of an artificial intelligence (AI) software (BoneMetrics, Gleamer) in performing automated measurements on weight-bearing forefoot and lateral foot radiographs. METHODS: Consecutive forefoot and lateral foot radiographs were retrospectively collected from three imaging institutions. Two senior musculoskeletal radiologists independently annotated key points to measure the hallux valgus, first-second metatarsal, and first-fifth metatarsal angles on forefoot radiographs and the talus-first metatarsal, medial arch, and calcaneus inclination angles on lateral foot radiographs. The ground truth was defined as the mean of their measurements. Statistical analysis included mean absolute error (MAE), bias assessed with Bland-Altman analysis between the ground truth and AI prediction, and intraclass coefficient (ICC) between the manual ratings. RESULTS: Eighty forefoot radiographs were included (53 ± 17 years, 50 women), and 26 were excluded. Ninety-seven lateral foot radiographs were included (51 ± 20 years, 46 women), and 21 were excluded. MAE for the hallux valgus, first-second metatarsal, and first-fifth metatarsal angles on forefoot radiographs were respectively 1.2° (95% CI [1; 1.4], bias = - 0.04°, ICC = 0.98), 0.7° (95% CI [0.6; 0.9], bias = - 0.19°, ICC = 0.91) and 0.9° (95% CI [0.7; 1.1], bias = 0.44°, ICC = 0.96). MAE for the talus-first, medial arch, and calcaneal inclination angles on the lateral foot radiographs were respectively 3.9° (95% CI [3.4; 4.5], bias = 0.61° ICC = 0.88), 1.5° (95% CI [1.2; 1.8], bias = - 0.18°, ICC = 0.95) and 1° (95% CI [0.8; 1.2], bias = 0.74°, ICC = 0.99). Bias and MAE between the ground truth and the AI prediction were low across all measurements. ICC between the two manual ratings was excellent, except for the talus-first metatarsal angle. CONCLUSION: AI demonstrated potential for accurate and automated measurements on weight-bearing forefoot and lateral foot radiographs.

Revision of the 1994 World Health Organization T-score definition of osteoporosis for use in older East Asian women and men to reconcile it with their lifetime risk of fragility fracture.

The 1994 WHO criterion of a T-score ≤ -2.5 for densitometric osteoporosis was chosen because it results in a prevalence commensurate with the observed lifetime risk of fragility fractures in Caucasian women aged ≥ 50 years. Due to the much lower risk of fragility fracture among East Asians, the application of the conventional WHO criterion to East Asians leads to an over inflated prevalence of osteoporosis, particularly for spine osteoporosis. According to statistical modeling and when a local BMD reference is used, we tentatively recommend the cutpoint values for T-score of femoral neck, total hip, and spine to be approximately -2.7, -2.6, and -3.7 for Hong Kong Chinese women. Using radiographic osteoporotic vertebral fracture as a surrogate clinical endpoint, we empirically demonstrated that a femoral neck T-score of -2.77 for Chinese women was equivalent to -2.60 for Italian women, a spine T-score of -3.75 for Chinese women was equivalent to -2.44 for Italian women, and for Chinese men a femoral neck T-score of -2.77 corresponded to spine T-score of -3.37. For older Chinese men, we tentatively recommend the cutpoint values for T-score of femoral neck, total hip, and spine to be approximately -2.7, -2.6, and -3.2. With the BMD reference published by IKi et al. applied, T-score of femoral neck, total hip, and spine of -2.75, -3.0, and -3.9 for Japanese women will be more in line with the WHO osteoporosis definition. The revised definition of osteoporosis cutpoint T-scores for East Asians will allow a more meaningful international comparison of disease burden.

Statin use and longitudinal changes in quantitative MRI-based biomarkers of thigh muscle quality: data from Osteoarthritis Initiative.

OBJECTIVE: To assess whether changes in MRI-based measures of thigh muscle quality associated with statin use in participants with and without/at-risk of knee osteoarthritis. METHODS: This retrospective cohort study used data from the Osteoarthritis Initiative study. Statin users and non-users were matched for relevant covariates using 1:1 propensity-score matching. Participants were further stratified according to baseline radiographic knee osteoarthritis status. We used a validated deep-learning method for thigh muscle MRI segmentation and calculation of muscle quality biomarkers at baseline, 2nd, and 4th visits. Mean difference and 95% confidence intervals (CI) in longitudinal 4-year measurements of muscle quality biomarkers, including cross-sectional area, intramuscular adipose tissue, contractile percent, and knee extensors and flexors maximum and specific contractile force (force/muscle area) were the outcomes of interest. RESULTS: After matching, 3772 thighs of 1910 participants were included (1886 thighs of statin-users: 1886 of non-users; age: 62 ± 9 years (average ± standard deviation), range: 45-79; female/male: 1). During 4 years, statin use was associated with a slight decrease in muscle quality, indicated by decreased knee extension maximum (mean-difference, 95% CI: - 1.85 N/year, - 3.23 to - 0.47) and specific contractile force (- 0.04 N/cm2/year, - 0.07 to - 0.01), decreased thigh muscle contractile percent (- 0.03%/year, - 0.06 to - 0.01), and increased thigh intramuscular adipose tissue (3.06 mm2/year, 0.53 to 5.59). Stratified analyses showed decreased muscle quality only in participants without/at-risk of knee osteoarthritis but not those with established knee osteoarthritis. CONCLUSIONS: Statin use is associated with a slight decrease in MRI-based measures of thigh muscle quality over 4 years. However, considering statins' substantial cardiovascular benefits, these slight muscle changes may be relatively less important in overall patient care.

Advances in osteoarthritis imaging.

PURPOSE OF REVIEW: Imaging plays a pivotal role for diagnosis, follow-up and stratification of osteoarthritis patients in clinical trials and research. We aim to present an overview of currently available and emerging imaging techniques for osteoarthritis assessment and provide insight into relevant benefits and pitfalls of the different modalities. RECENT FINDINGS: Although radiography is considered sufficient for a structural diagnosis of osteoarthritis and is commonly used to define eligibility of patients for participation in clinical trials, it has inherent limitations based on the projectional nature of the technique and inherent challenges regarding reproducibility in longitudinal assessment. MRI has changed our understanding of the disease from 'wear and tear' of cartilage to a whole organ disorder. MRI assessment of structural changes of osteoarthritis includes semi-quantitative, quantitative and compositional evaluation. Ultrasound is helpful in evaluating the degree of synovitis and has value in the assessment particularly of the patella-femoral joint. Recent development of computed tomography technology including weight-bearing systems has led to broader application of this technology in a research context. SUMMARY: Advances in MRI technology have resulted in a significant improvement in understanding osteoarthritis as a multitissue disease.

Emerging Quantitative Imaging Techniques in Sports Medicine.

This article describes recent advances in quantitative imaging of musculoskeletal extremity sports injuries, citing the existing literature evidence and what additional evidence is needed to make such techniques applicable to clinical practice. Compositional and functional MRI techniques including T2 mapping, diffusion tensor imaging, and sodium imaging as well as contrast-enhanced US have been applied to quantify pathophysiologic processes and biochemical compositions of muscles, tendons, ligaments, and cartilage. Dual-energy and/or spectral CT has shown potential, particularly for the evaluation of osseous and ligamentous injury (eg, creation of quantitative bone marrow edema maps), which is not possible with standard single-energy CT. Recent advances in US technology such as shear-wave elastography or US tissue characterization as well as MR elastography enable the quantification of mechanical, elastic, and physical properties of tissues in muscle and tendon injuries. The future role of novel imaging techniques such as photon-counting CT remains to be established. Eventual prediction of return to play (ie, the time needed for the injury to heal sufficiently so that the athlete can get back to playing their sport) and estimation of risk of repeat injury is desirable to help guide sports physicians in the treatment of their patients. Additional values of quantitative analyses, as opposed to routine qualitative analyses, still must be established using prospective longitudinal studies with larger sample sizes.

Gadolinium Deposition in the Rat Brain Measured with Quantitative MRI versus Elemental Mass Spectrometry.

Background T1-weighted MRI and quantitative longitudinal relaxation rate (R1) mapping have been used to evaluate gadolinium retention in the brain after gadolinium-based contrast agent (GBCA) administration. Whether MRI measures accurately reflect gadolinium regional distribution and concentration in the brain remains unclear. Purpose To compare gadolinium retention in rat forebrain measured with in vivo quantitative MRI R1 and ex vivo laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) mapping after gadobenate, gadopentetate, gadodiamide, or gadobutrol administration. Materials and Methods Adult female Sprague-Dawley rats were randomly assigned to one of five groups (eight per group) and administered gadobenate, gadopentetate, gadodiamide, gadobutrol (2.4 mmol/kg per week for 5 weeks), or saline (4.8 mL/kg per week for 5 weeks). MRI R1 mapping was performed at baseline and 1 week after the final injection to determine R1 and ΔR1. Postmortem brains from the same rats were analyzed with LA-ICP-MS elemental mapping to determine regional gadolinium concentrations. Student t tests were performed to compare results between GBCA and saline groups. Results Rats that were administered gadobenate showed gadolinium-related MRI ΔR1 in 39.5% of brain volume (ΔR1 = 0.087 second-1 ± 0.051); gadopentetate, 20.6% (ΔR1 = 0.069 second-1 ± 0.018); gadodiamide, 5.4% (ΔR1 = 0.055 second-1 ± 0.019); and gadobutrol, 2.2% (ΔR1 = 0.052 second-1 ± 0.041). Agent-specific gadolinium-related ΔR1 was detected in multiple forebrain regions (neocortex, hippocampus, dentate gyrus, thalamus, and caudate-putamen) in rats treated with gadobenate or gadopentetate, whereas rats treated with gadodiamide showed gadolinium-related ΔR1 in caudate-putamen. By contrast, LA-ICP-MS elemental mapping showed a similar regional distribution pattern of heterogeneous retained gadolinium in the forebrain of rats treated with gadobenate, gadopentetate, or gadodiamide, with the average gadolinium concentration of 0.45 µg · g-1 ± 0.07, 0.50 µg · g-1 ± 0.10, and 0.60 µg · g-1 ± 0.11, respectively. Low levels (0.01 µg · g-1 ± 0.00) of retained gadolinium were detected in the forebrain of gadobutrol-treated rats. Conclusion Differences in in vivo MRI longitudinal relaxation rate versus ex vivo elemental mass spectrometry measures of retained gadolinium in rat forebrains suggest that some forms of retained gadolinium may escape detection with MRI. © RSNA, 2022 Online supplemental material is available for this article.